Multi-strain probiotic combinations differentially inhibit Salmonella serovars

This study examined the antagonistic activity of Lactiplantibacillus plantarum, Bifidobacterium bifidum, Propionibacterium freudenreichii, and Propionibacterium jensenii against seven Salmonella serovars. Using a co-culture model, 11 different combinations of the four probiotic strains (PS) were prepared and used as treatments. Organic acids production (lactic, acetic, propionic, butyric, and valeric acids) was measured as individual strains and in each of the 11combinations, demonstrating that multi-strain preparations produced significantly higher acid concentrations, particularly lactic (up to 781 mM), propionic (up to 595 mM), and valeric acids (up to 168 mM). The pH of the culture media dropped significantly after 24 h from about 6.72 to 3.85. Salmonella reductions varied by PS mixture tested, ranging from about 2 Log₁₀ to up to 8 Log₁₀ CFU/mL. The most effective combination against Salmonella was the four-PS mixture, with non-detectable levels after treatment. These findings suggest that multi-strain probiotic treatments act synergistically to enhance organic acid production, thereby serving as antimicrobials, and identify the most effective probiotic combinations for reducing Salmonella populations. The demonstrated effectiveness of PS mixes highlights their potential as an innovative alternative to conventional antimicrobials in livestock systems. By addressing both food safety and antimicrobial resistance, these findings advance One Health and offer practical applications for improving animal production and public health.